setting for printing in Fresco

Hi @Nichole30963543608o , The easiest way to make sure that your artwork stays in the desired gamut in a program that doesn't have any colour management is using a palette of printable colours. Painting with those colours will produce colours that are likely to stay within your desired gamut. It's important to keep in mind that some blending modes might break this, so be careful when you use them (specially the aditive ones, the ones that make the result brighter than the original colour).

That being said, this only applies to colours you want to be precisely reproduced on paper. Colour management usually does a decent job converting from sRGB to the most common CMYK spaces. The only problematic areas are colours with maximum saturation, as they are closer to the pure primaries in the source colorspace, and those aren't printable (green, specially).
As a general rule, I'd say that you'll want to be careful with satuated green to blue shades. Those are the ones that suffer the most when you convert from RGB to CMYK, as cyan ink is nowhere close to a pure saturated RGB cyan.
Saturated magentas are going to suffer the same problem, so the shades between blue and magenta are problematic too, although less frecuent in artwork than green-cyan-blue shades.
Shades leaning towards yellow (from red, to orange, to yellow and from green, lime to yellow) will be easier to reproduce, as yellow ink can be bright enough to be closer to your RGB yellow.

So, long story short:
- Use a palette of printable colours, specially for your saturated greens, blues and magentas. Those are less likely to be printable, so figure out what's the most saturated printable shade you can get and create a palette for them so you can pick your colours from there.
- Keep an eye on the effect of blending modes. If they brighten colours making them more saturated than the colours in your palette, dial their saturation down so they stay printable (specially blues, cyans, greens, and magentas).

Now, regarding the 100% black requirement, let me say it's a quite stupid one. What if you were an artist who does photographic collages? Or even, what if you are a photographer? How do you paint 100% black there?
That's quite ridiculous, specially because colour management will automatically take care of your RGB black and create a rich black that uses the four plates to produce a rich and deep black that is impossible to obtain with a 100% black only plate.
Sure, there are very specific situations where controling the black genereation is desirable (if your artwork is mostly black) and deciding how the RGB black will be separated into CMYK makes sense, but again that doesn't require to use CMYK from scratch. Color profiles with specific black generation features can be used.
I'm not sure what so say about this. If the provider requires this it is probably a good idea to look around and find a new provider. Remember, if your artwork was a photo that requirement would be ridiculous.